Complement Components and Their Activation Products in Pleural Fluid

¹ From the Department of Pulmonary Diseases and Clinical Allergology, Turku University, Finland
² From the Department of Turku University Hospital, and the Department of Medical Microbiology, Turku University, Finland

Eija-Riitta Salomaa, MD, Department of Pulmonary Diseases and Clinical Allergology, Turku University Hospital, FIN-21540 Preitilä, Finland; e mail eirisa{at}utu.fi

Study objectives: The aim of this study was to determine the role of complement components in pleural effusion measured with novel markers of complement activation, to assess which pathway of activation is predominant in different diseases, and to find out whether the analysis of complement components and their activation products could help in diagnostic procedure differentiating the etiologies of pleural effusion.

Patients: The study population consisted of 71 patients who had pleural effusion secondary to tuberculosis (n=23), rheumatic disease (n=10), or malignancy (n=38).

Measurements: Complement components and their activation products, including the soluble terminal complex SC5b-9, were measured in plasma and pleural fluid.

Results: In all patients with rheumatic pleurisy, pleural fluid SC5b-9 was higher than 2 AU/mL and in all patients with malignant pleural fluid it was lower than 2 AU/mL. The mean level of SC5b-9 in rheumatic pleural effusion was also significantly higher than in tuberculosis. In addition, the concentrations of pleural fluid C3 and C4 were significantly lower and the ratio C4d/C4 was significantly higher in rheumatic compared with tuberculous or malignant pleurisy. In plasma, both SC5b-9 and Cls-Clr-C1INH-complexes were significantly higher in rheumatic subjects than in other patients. In stepwise multinominal logistic regression analyses, the most significant predictors for rheumatic pleural fluid were high pleural fluid SC5b-9 and low C4.

Conclusions: These observations indicate that the complement cascade is activated through both the classic and the alternative pathways in rheumatic pleurisy. Determinations of SC5b-9 and C4d/C4 in pleural fluid were the best variables differentiating rheumatic, tuberculous, and malignanteffusions.

Key Words: complement activation • malignancy • pleural effusion • pleural fluid • rheumatoid arthritis • tuberculosis

Submitted on November 11, 1997
Accepted on March 30, 1998

This article has been cited by other articles:

				B L Man and C C Mok Serositis related to systemic lupus erythematosus: prevalence and outcome Lupus, October 1, 2005; 14(10): 822 - 826. [Abstract] [PDF]

				N A Maskell and R J A Butland BTS guidelines for the investigation of a unilateral pleural effusion in adults Thorax, May 1, 2003; 58(90002): ii8 - 17. [Full Text]